Arthropods make up over 75% of the world's animal species. Arthropods include animals such as insects, crustaceans and arachnids. The largest group of Arthropods are the insects. The next largest group are the crustaceans, including lobsters and crabs. The arachnids include spiders and ticks. Other Arthropods include centipedes and millipedes.

Arthropods have limbs with joints that allow them to move. They also have an exoskeleton, which is a hard, external skeleton. Their body cavity contains the nervous system, circulatory system, reproductive system and digestive system.

Crustaceans Arachnids Insects